Sega Dreamcast What was the "official" name of the Dreamcast shlells?

You know, the replacement shells / skins / covers / or whatever? What were they called?

and what happened to them all? When Sega went out... everywhere was littered with them... but in the last couple years, I've been trying to get some to put in the shop, and .... they are hard to find... what is the deal there?

†B†V† :hat

Shells I think

Yet ya, you are right, there was loads of them in the past. I wanted a Green one, but never got around to getting one